3i8 CORALS AND CORAL ISLANDS. 



Keeling's is another outlying atoll south-west of southern 

 Sumatra and far out toward mid-ocean. 



The probability is, therefore, that both the central Atlantic 

 and Indian Oceans were regions of this subsidence, like the 

 central Pacific, and that the absence of islands over a large 

 part of their interiors may be a consequence of it. A rate of 

 sinking exceeding five feet in a thousand years (if the esti- 

 mate on page 215 is right) would have buried islands and 

 reefs together in the ocean ; while, with a slower rate, the 

 reefs might have kept themselves at the water's surface. So 

 small may have been the difference of rate in the great move- 

 ment that covered the Pacific with coral islands, but left the 

 Indian Ocean a region of comparatively barren waters, with 

 some '^ half-drowned " atolls, and the central Atlantic almost 

 wholly a blank. 



While thus seeming to prove that all the great oceans have 

 their buried lands, we are far from establishing that these lands 

 were oceanic continents. For as the author has elsewhere 

 shown, the profoundest facts in the earth's history prove that 

 the oceans have always been oceans. These lands in all pro- 

 bability were, for the most part, volcanic islands or summits of 

 volcanic ranges, for of this nature are all the islands over the 

 interior of either ocean that are not of coral origin. 



The course of argument leads us to the belief that a very 

 large number of islands, more than has been supposed, lie 

 buried in the ocean. Coral islands give us the location of 

 many of these lands : but still we know little of the extent to 

 which the earth's ranges of heights, or at least of volcanic 

 peaks, have disappeared through oceanic subsidence. Recent 

 dredgings and soundings have proved that the bottom of the 

 oceanic basin has little of the diversity of mountain chains 

 and valleys that prevails over the continents ; and, through 

 this observation (and also by the discovery that some ancient 

 tj^es of animal life, supposed to have been long extinct, are 

 perpetuated there), they have afforded new demonstration of 

 the proposition, above stated, that the oceans have always been 

 oceans. But while the facts do not imply the existence deep 



